The Effect of Ultraviolet Radiation on Production of Antioxidant Compounds from Bioprospected Acid Tolerant Microalgae Used to Mitigate Industrial CO 2

Abstract

Controlling light exposure (wavelength and intensity) has been shown to increase the cellular production of antioxidants in some species of microalgae. However, these light stress studies do not typically examine extremophiles, which have been shown to produce antioxidants as a defense mechanism. This study aims to examine the effect of ultraviolet radiation (UVR) on the production of natural antioxidant compounds (carotenoids, chlorophyll a, and chlorophyll b) in extremophiles, with the ultimate goal of improving the feasibility of industrial CO₂ mitigation. Three strains of microalgae were bioprospected from low pH (<4) mining impacted water bodies in Ontario, Canada. This study found that the bioprospected strains naturally produce higher levels of antioxidant compounds compared to culture collection strains. However, decreasing the pH, as would happen with industrial off-gas application, resulted in a decreased concentration of antioxidant compounds and activity, with the exception: strain M2 maintained high activities at both low and unregulated pH. Three UVR treatments were tested, consisting of 10 h of UVR exposure and different recovery periods. Treatments resulted in increased antioxidant concentrations in samples with initially low concentrations, with these concentrations continuing to increase for up to 48 h after UVR exposure. A concurrent increase in antioxidant activity was also determined based on ABTS radical scavenging activity and ferric reducing power. Furthermore, this study identifies a promising strain (M2) that could simultaneously produce health beneficial compounds and mitigate industrial CO₂ emissions.